In late March, Johnny Wee encountered a Greater Racket-tailed Drongo (Dicrurus paradisus) at the Bukit Timah Nature Reserve. He witnessed the bird catching a large forest cockroach (Pseudophoraspis nebulosa) (left).
The bird obviously caught the cockroach by the head, holding it firmly in its bill. It then tossed the insect into the air to swallow it head-first. As soon as it swallowed the insect, it spitted it out. Obviously there must be something unpleasant with the cockroach to force the drongo spit it out.
Prof Cheong Loong Fah confirmed the identification of the cockroach and added that some cockroaches are known to have chemical defenses.
Yes, certain cockroaches possess repellent chemicals that are foul-smelling, bad tasting, simply irritating or even have the ability to cause pain. Such chemicals are also known to be produced by some termites, earwigs, stick insects and beetles.
Several species of cockroach have been known to produce an anal secretion that quickly cripples worker ants that attack them. The adults of the subtropical cockroach Eurycotis floridana, emit a defensive chemical spray that can deter small mammals.
If this particular cockroach is inedible because of some reason or other, it is to be expected that this drongo would have learnt its lesson and avoid such cockroaches in future. Birds learn fast to avoid distasteful or inedible foods.
Drongos are insectivorous, feeding on beetles, large ants, termites, green bees, caterpillars, stick insects, grasshoppers, dragonflies and cicadas. The bird hunts by sallying from a lookout perch, to return to the same perch to eat its prey.
1. O’Connell, T.J. & Reagla, N.Z. (2002). Is the chemical defense of Eurycotis floridana a deterrent to small mammal predators? Florida Scientist 65:245-249.
2. Smythies, B. E. (1999). Birds of Borneo. Kota Kinabalu: Natural History Pub. (Borneo) Sdn. Bhd. & The Sabah Society. 4th ed, revised by G. W. H. Davison.
3. Wells, D.R. (2007). The birds of the Thai-Malay Peninsular. Vol. II, Passerines. Christopher Helm, London.